The present invention relates to a process for preparing phenols and N-acylanilines substituted with fluorine in the 2-, 4- or 6-position and to N-fluoropyridinium salt fluorinating agents useful in the process.
Halophenols and N-acylhaloanilines substituted in the 2-, 4-, or 6-position and with fluorine and with one or more bromine or chlorine are valuable intermediates in the preparation of herbicides, insecticides, fungicides, and pharmaceuticals. Many such compounds are known and processes for their preparation involving diazotization chemistry and halogen exchange with potassium or cesium fluoride chemistry have been reported. Such processes are difficult to carry out and often produce large amounts of waste. Because the subject compounds have been accessible only through relatively complex, multistep processes, their utility as intermediates has been confined to situations where the final product commands a very high price. It would be of considerable interest to discover a simple process for the preparation of fluorohalophenols and fluorohaloacylanilides which has the potential of providing such compounds to industry at a cost that would make them suitable as intermediates for products with other applications. Similarly, it would be of considerable interest to discover fluorinating agents useful in such processes.
It has recently been reported (European Application 204535, published Dec. 10, 1986) that phenol, 4-t-butylphenol, and 4-(methoxycarbonylmethyl)phenol and acetanilide react with certain N-fluoropyridinium salts to produce derivatives fluorinated in the 2-position and, in the cases of phenol and acetanilide, the 4-position. The fluorination of chloro and fluoro substituted compounds, however, typically involves replacement of the halogen by fluorine as a major reaction.